Tractor hoist



April 1, 1952 D. K. STRUTHERS ET AL 2,591,662

TRACTOR HOIST Filed June 6, 1946 Ina/anions" flarzaZd/xiiruhea 6603 96 l ijaroeci'ff- Patented Apr. 1, 1952 TRACTOR HOIST Donald K. Struthers and George W. Schroeder,

Des Moines, Iowa,

assignors to Harry Ferguson,

Inc., Detroit, Mich., a corporation of Delaware Application June 6, 1946, Serial No. 674,708

11 Claims.

This invention relates to tractor hoists.

An object of the invention is the provision of a hoist which is capable of lifting great loads, and yet is exceedingly simple and strong and can be lifted and manipulated by one man.

Another object is to provide a hoist having a minimum of moving parts, reducing the likelihood of wear. There is only one moving part on the hoist proper, with a few other moving parts necessary in adapting it to a tractor.

A further object of the invention is the provision of a novel means for applying power for lifting the hoist. A mechanical advantage is obtained which varies as the moment of force of the load being lifted varies. When the hoist is carrying a load in lowered or horizontal position, the load exerts its greatest force; in this position lifting power is applied at an extended e point from the pivot of the hoist, and as the hoist is elevated the load moves toward a vertical line through the pivot point, with increasingly less turning force on the hoist, and at the same time the point of application of the lifting force moves nearer the pivot point of the hoist.

Another advantage of the invention is that the hoist is telescopic for varying its load lifting capacity.

A still further advantage is that the hoist cannot be lifted too far, or swung over center, with consequent injury to the operator.

An additional advantage of the invention is that the hoist can be applied in only one way, eliminating the possibility of incorrectly applying it.

Another advantage is that the hoist can be adapted to the power lift system which is originally supplied with a tractor.

A further advantage is that a load may be lifted, and transported by the tractor, by means of the hoist.

With these and other objects in view, our invention consists in the construction, arrangement and combination of the various parts of our device whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in our claims and illustrated in the accompanying drawings, wherein:

Fig. 1 is a perspective view of the device applied to a tractor, the tractor being partially broken away; and

Fig. 2 is a side view of the same.

Referring in detail to the drawings the tractor hoist of our invention includes a telescopic boom 1 2 having an outer member I 4 and an inner member l6 slidable in the outer member.

The outer 2 end of the inner member 16 is curved as shown at [8 and has a forked extremity 20 from which depends a hook 22 for carrying a load.

Welded to the inner end of the outer mem-' ber I4 are lugs 24 forming a bracket by which the boom is pivoted to the tractor frame 26 by means of a pin 28. The pin 28 is a simple pin provided with a cotter key for quick attaching and detaching. The outer end of the outer member I4 is provided with a reinforcing col1ar 30 through which a set screw 32 is threaded for securing the two members of the telescopic boom I2 in relative position.

As will be observed the boom I2 is'swingable about the pivot 28, and for the purpose of swing-' ing the boom, a strut structure 34 is secured adjacent the pivotal end thereof. The strut struc ture 34 comprises two pairs of struts 36 and 38.

One of each pair of struts is welded to the bracket 24 as indicated at 40, or at any convenient point near the pivotal end of the boom; and the other one of each pair of struts is welded to the outermember 1 4 as indicated at 42; the point 42 being extended outwardly from the pivotal end ofv the boom. The individual struts of each pair 36 and 38 converge to apexes 44 and 46, and the two pairs diverge downwardly so that the apexes 44 and 46 are spaced apart. Secured to and extending between the apexes 44 and 46 is a transverse member 48, for rendering the strut 'struc ture rigid. The ends of the transverse member 48 extend outwardly beyond the apexes 44 and 46 as indicated at 58.

Pivoted on the outer ends 58 of the transvere; member 48 are two swingable arms 52 by means of eyes formed on the swingable arms, which fit over the ends 58.

arms 52 is another transverse member 54 which also extends outwardly beyond the swingable arms 52 as indicated at 56.

A pair of power lift arms 58 are pivoted at one end on the tractor frame as indicated at 68 and are pivoted at their other ends tothe extremities- 56 respectively of the transverse member 64.,

Cotter keys, or other simple means, are employed for retaining the outer ends of the power lift arms 58 on the ends 56.

one of which is provided on tractor frame.

. The elevating arms 68 are standard power takeoff operating armssupplied witlithe tractor and" Welded to and extending between the free ends of the pivoted swingable 3 are operated through their pivotal points H! by a. power take-off device in the tractor.

To provide added strength for the boom a bracing member is provided. This bracing member includes a rod 1'2 having one end welded at the inner end of the outer member l4, and having its other end welded to the outer end of the outer member M. A spacing member 14 is secured between the boom and the rod 12, substantially centrally of the ends of the rod.

It will be noted that when the hoist is in place the strut structure 34 is on the underside of the hoist and the reinforcing rod 12 is on the opposite, or upperside.

Use and. operation The actual handling of a load is done in a customary manner by means of lowering and raising the hoist with a load secured on the hook 22. When the load is thus raised it may be'carried about by the tractor conveniently and the tractor is not limited to handling loads in a localized area.

To elevate the hoist the elevating arms 68 are rotated clockwise, lifting the links 62 and thereby lifting the power lift arms 58. The power lift arms 58 apply force through the swingable arms 52 toelevate the hoist.

The operation of the hoist embodies a new adaptation of applying mechanical advantage. It will be noted in Fig. 2 that when the hoist is lowered it is in approximately a horizontal position. At this point a load on the end of the hoist exerts its greatest turning force, that is, the direction of the force of the load is tan gential to the path of movement of the free end of the hoist.

When the hoist is in lowered or horizontal position the swingable arms 52 are also in substantial horizontal position, and in this position the arms 52 extend substantially perpendicular to the direction of motion of the pivot points 56. Great mechanical advantage is thereby exerted on the swingable arms 52 when the turning force of the load on the hoist is greatest. When the hoist is elevated the pivot points 56 travel through the are 19 and thepivot points 50 travel through the are 18, whereby the swingable arms 52 reach and pass through a vertical position.

When the hoist is elevated the load approaches a vertical line extending through the pivotal point of the hoist, and the direction of force of the load is more nearly toward the pivotal point of the hoist, and thereby its turning force is less. This change in the effect of the load requires less force in continuing to elevate the hoist. In the continued elevating of the hoist, the pivot point 50 travels at a greater rate than the pivot point 56, resulting in a decrease in mechanical advantage applied. It will therefore be seen that the lifting force applied to the boom tends to remain approximately constant, that is, when the turning force of the load is at its greatest, the mechanical advantage applied in elevating the hoist is greatest, and as the turning force of the load decreases, the mechanical advantage applied also decreases. This phenomenon is a result of the fact that the power lift arms '58 are pivoted on the tractor frame below the pivotal point of the boom.

By extending the pivot points 58 from the boom, or in other words, extending the length of the strut structure 34, the lifting capacity of the hoist can be varied. Also, by varying the length of the swingable arms 52, the lifting capacity of the hoist may be varied.

Varying the adjustable length of the telescopic boom I2 is another manner in which the lifting capacity of the hoist can be varied.

The device of our invention is a light and simple device, and can easily be handled by one man. It is easily attachable to and detachable from the tractor, and when attached, the user is assured that it will be applied correctly, because there is only one way to apply it.

It will be understood by one skilled in the art that the word hoist" as employed in the specification and claims is a general one having its ordinary dictionary meaning, namely, that by which anything is raised, lifted or elevated. It will be apparent, therefore, that the invention is not limited to the specific construction illustrated which constitutes merely the preferred embodiment and in which an extended boom and book are employed for raising the load. On the contrary, the invention obviously includes within its scope devices inwhich a weighty'load is fastened to the pivoted member l2 by means, other. than a hook, and such fastening may be of: a permanent rather than a temporary nature.

It will also be recognized by one skilled in the art that the present invention is not limited to the particular length of the boom I2 shown in the drawing but includes members. performing an equivalent function which are much shorter in length. The important feature is that the mechanical advantage between the draft links and the pivoted member or boom is progressively decreased as such pivoted member is swung up.- wardly. The term boom therefore is employed merely for purposes of convenience as designating any upwardly swinging member which is. pivoted above the point of pivoting of the tractor draft. links.

While we have shown a particular embodiment of our invention, it will be understood of course. that we do not wish to be limited thereto since many modifications may be made, and we there-. fore contemplate by the claims appended hereto to cover any such modifications or substitutions of mechanical equivalents as fall within the true spirit and scope of our invention without sacrificing any of its advantages.

We claim as our invention:

1. A tractor hoist comprising, in combination. a boom adapted to be pivoted on a tractor, a strut structure on said boom extending transversely therefrom, a swingable arm pivoted at one end on the outer end of said strut structure, a power lift arm having one end pivoted on'the free end of said swingable arm and its other end pivoted on the tractor frame, and a link pivoted intermediate the ends of said power lift arm and adapted to be connected with power means on the tractor for swinging said power lift arm and thereby swinging said boom.

2. A tractor hoist comprising, in combination, a boom adapted to be pivoted on a tractor'for vertical swinging between a substantially horizontal lowered position and a generally upright elevated position, a strut structure on said boom extending transversely therefrom, a sw n able arm pivoted at one end on the outer end of said strut structure, a power lift arm pivoted at one end on the tractor and at the other end on the free end of said swingable arm, and means powered by the tractor operating through said power lift arm for elevating the hoist, the pivots of said boom and said power lift arm being spacfidapart I the tractor and operating through said power lift arm and movable member for elevating the boom, the pivots of said boom and said arm being disposed so that the point of connection of said power lift arm with said movable member moves progressively toward the pivot point of'said boom as the load being lifted by the boom moves' toward a vertical line through the pivot point of said boom.

' 4. In a-hoist attachment for a tractor having a pair of power elevated draft links trailingly pivoted on the rear end portion thereof and having a pivot connection arranged on said rear end portion above said links, the combination comprising a boom having means thereon for pivoting the same to the pivot connection on said tractor, boom supporting means including a member extending generally downwardly from the boom for connection to the trailing ends of said tractor draft links, the connection for said supporting means including members movable relative to the supporting means to permit relative movement between the trailing ends of said draft links and said boom, so that said boom is raised upon elevation of said links with a mechanical advantage which is a maximum with the boom in a lowered position and which decreases progressively as said boom is elevated toward a vertical position.

5. In ahoist attachment for a tractor having a pair of power elevated draft links trailingly pivoted on the rear end portion thereof and having a pivot connection arranged on said rear end portion above said links, the combination comprising a boom having means thereon for pivoting the same to the pivot connection on said tractor. boom supporting means including a strut rigid with said boom and extending generally downwardly therefrom, connecting elements on the lower end of said supporting means for engaging the trailing ends of said tractor draft links, and means securing said connecting elements to said supporting means for relative movement with respect to said links in a direction generally parallel to the plane of said links so that the mechanical advantage between .said link with a mechanical advantage which is ia maximum with the boom in a lowered position and which decreases progressively as said boom is elevated toward a vertical position.

7. In a hoist attachment for a tractor having, a pair of power elevated draft links trailingly {pivoted on the rear end portion thereof and having a pivot connection arranged on said rear end portion above said links, the combination 10.

the base portion thereof to the pivot conneccomprising a boom having means for pivoting tion on said tractor, boom supporting means-ineluding astrut extending generally downwardly from the boom and rigidly joined thereto, means :including a link for pivotally connecting said strut to the trailing ends of said tractor draft links, said link means permitting relative movement between the trailing ends of said draft links and said boom, so that said boom is raised upon elevation of said links with a mechanical advantage which decreases progressively as said boom is elevated toward a vertical position 8. In a hoist attachment for a tractor having .vertically swingable draft linkage trailingly pivoted on the rear end portion thereof, a power lift mechanism for lifting such linkage, and having a pivot connection arranged on said rear end portion above said linkage, the combination comprising: a boom having means thereon for pivoting the same to the pivot connection on said tractor, means for suspending a load from said boom, boom supporting means operatively connected between said boom and said draft linkage so that the boom is elevated upon power elevation of said draft linkage, said supporting means including a member rigid with the boom and a connecting element interposed between said member and the draft links to allow relative movement between the trailing ends of the draft links and said boom so that the radius of the line of action of the elevating force on said boom decreases relative to the radius of the line of action of the elevating force on said draft linkage as the boom is swung upwardly thus causing a progressive decrease in mechanical advantage of the power lift mechanism relative to the suspended load as an incident to joint upward said links and said boom is varied as the boom is swung upwardly.

6. In a hoist attachment for a tractor having a power elevated draft link trailingly pivoted on the rear end portion thereof and having a pivot said'draft link and said boom and permitting relative movement between the connected parts so that said boom is raised upon elevation of,

swinging movement of said linkage and boom.

9. A boom structure comprising, in combination, an elongated boom member, a strut extending transversely therefrom, said strut including a first pair of angularly disposed members connected together at one end and having their other ends rigidly secured to said boom member at points spaced apart axially thereof, a second pair of angularly disposed members connected together at one end and having their other ends rigidly secured to said boom member adjacent said axially spaced points, said pairs of members diverging from each other to present their apexes in laterally spaced relation, and means including a pair of swingable links pivotally secured to the respective pairs of strut members adjacent their apexes for raising and lowering said boom member.

10. A boom structure comprising, in combination, an elongated boom member, a strut extending transversely therefrom, said strut including a first pair of angularly disposed members each connected to the other at one end and having their other ends rigidly secured to said boom member at points spaced apart axially thereof, a second pair of angularly disposed members connected together at one end and having their other ends rigidly secured to said elongated member at points spaced apart axially thereof, said pairs of members diverging from each other to present their apexes in laterally spaced relation, a transverse member secured between the apexes of said pairs of members, and operating links swingably mounted on opposite ends of said transverse member.

11. In a hoist attachment for a tractor having a power lift mechanism, the combination of an elongated boom, connecting means for pivotally supporting one end of said boom on the tractor, load suspending means adjacent the other end of said boom, a linkage interposed between the power lift mechanism of the tractor and said boomior swinging the boom between lowered and raised positions, said linkage including a strut structure rigid with said boom, a pair of links each pivotally connected to the other at one end and respectively pivoted at their other ends to the tractor and to said strut structure to provide a mechanical advantage in the transmission of force from the power lift mechanism of the tractor to said boom, the pivots of said links being spaced relative to the pivot for the boom so that the mechanical advantage provided by the linkage is at its maximum when the boom is in the lowered positions and decreases progressively as the boom is swung upwardly.

DONALD K. STRUTHERS. GEORGE W. SCHROEDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 678,393 Geery July 16, 1901 742,552 Anderson Oct. 27, 1903 1,458,739 Weber June 12, 1923 1,509,905 Salyards et a1 Sept. 30, 1924 1,649,574 Conway Nov. 15, 1927 1,941,952 Nickles Jan. 2, 1934 2,019,938 Stephens Nov. 5, 1935 2361,433 1949 Moulton et al. Feb. 8, 

